/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.beanutils.converters;

import org.apache.commons.beanutils.ConversionException;

/**
 * {@link org.apache.commons.beanutils.Converter} implementaion that handles conversion to and from <b>Boolean</b> objects.
 * {@link org.apache.commons.beanutils.Converter} implementaion that handles conversion to and from <b>java.lang.Boolean</b> objects.
 * <p>
 * Can be configured to either return a <i>default value</i> or throw a <code>ConversionException</code> if a conversion error occurs.
 * <p>
 * By default any object whose string representation is one of the values {"yes", "y", "true", "on", "1"} is converted to Boolean.TRUE, and string
 * representations {"no", "n", "false", "off", "0"} are converted to Boolean.FALSE. The recognised true/false strings can be changed by:
 * 
 * <pre>
 * String[] trueStrings = { &quot;oui&quot;, &quot;o&quot;, &quot;1&quot; };
 * String[] falseStrings = { &quot;non&quot;, &quot;n&quot;, &quot;0&quot; };
 * Converter bc = new BooleanConverter(trueStrings, falseStrings);
 * ConvertUtils.register(bc, Boolean.class);
 * ConvertUtils.register(bc, Boolean.TYPE);
 * </pre>
 * 
 * In addition, it is recommended that the BooleanArrayConverter also be modified to recognise the same set of values:
 * 
 * <pre>
 * Converter bac = new BooleanArrayConverter(bc, BooleanArrayConverter.NO_DEFAULT);
 * ConvertUtils.register(bac, bac.MODEL);
 * </pre>
 * 
 * </p>
 * 
 * <p>
 * Case is ignored when converting values to true or false.
 * </p>
 * 
 * @author Craig R. McClanahan
 * @version $Revision: 801644 $ $Date: 2009-08-06 14:38:56 +0100 (Thu, 06 Aug 2009) $
 * @since 1.3
 */
public final class BooleanConverter extends AbstractConverter {

    // ----------------------------------------------------------- Constructors

    /**
     * Create a {@link org.apache.commons.beanutils.Converter} that will throw a {@link ConversionException} if a conversion error occurs, ie the
     * string value being converted is not one of the known true strings, nor one of the known false strings.
     */
    public BooleanConverter() {
        super();
    }

    /**
     * Create a {@link org.apache.commons.beanutils.Converter} that will return the specified default value if a conversion error occurs, ie the
     * string value being converted is not one of the known true strings, nor one of the known false strings.
     * 
     * @param defaultValue
     *            The default value to be returned if the value being converted is not recognised. This value may be null, in which case null will be
     *            returned on conversion failure. When non-null, it is expected that this value will be either Boolean.TRUE or Boolean.FALSE. The
     *            special value BooleanConverter.NO_DEFAULT can also be passed here, in which case this constructor acts like the no-argument one.
     */
    public BooleanConverter(Object defaultValue) {
        super();
        if (defaultValue != NO_DEFAULT) {
            setDefaultValue(defaultValue);
        }
    }

    /**
     * Create a {@link org.apache.commons.beanutils.Converter} that will throw a {@link ConversionException} if a conversion error occurs, ie the
     * string value being converted is not one of the known true strings, nor one of the known false strings.
     * <p>
     * The provided string arrays are copied, so that changes to the elements of the array after this call is made do not affect this object.
     * 
     * @param trueStrings
     *            is the set of strings which should convert to the value Boolean.TRUE. The value null must not be present. Case is ignored.
     * 
     * @param falseStrings
     *            is the set of strings which should convert to the value Boolean.TRUE. The value null must not be present. Case is ignored.
     * @since 1.8.0
     */
    public BooleanConverter(String[] trueStrings, String[] falseStrings) {
        super();
        this.trueStrings = copyStrings(trueStrings);
        this.falseStrings = copyStrings(falseStrings);
    }

    /**
     * Create a {@link org.apache.commons.beanutils.Converter} that will return the specified default value if a conversion error occurs.
     * <p>
     * The provided string arrays are copied, so that changes to the elements of the array after this call is made do not affect this object.
     * 
     * @param trueStrings
     *            is the set of strings which should convert to the value Boolean.TRUE. The value null must not be present. Case is ignored.
     * 
     * @param falseStrings
     *            is the set of strings which should convert to the value Boolean.TRUE. The value null must not be present. Case is ignored.
     * 
     * @param defaultValue
     *            The default value to be returned if the value being converted is not recognised. This value may be null, in which case null will be
     *            returned on conversion failure. When non-null, it is expected that this value will be either Boolean.TRUE or Boolean.FALSE. The
     *            special value BooleanConverter.NO_DEFAULT can also be passed here, in which case an exception will be thrown on conversion failure.
     * @since 1.8.0
     */
    public BooleanConverter(String[] trueStrings, String[] falseStrings, Object defaultValue) {
        super();
        this.trueStrings = copyStrings(trueStrings);
        this.falseStrings = copyStrings(falseStrings);
        if (defaultValue != NO_DEFAULT) {
            setDefaultValue(defaultValue);
        }
    }

    // ----------------------------------------------------- Static Variables

    /**
     * This is a special reference that can be passed as the "default object" to the constructor to indicate that no default is desired. Note that the
     * value 'null' cannot be used for this purpose, as the caller may want a null to be returned as the default.
     * 
     * @deprecated Use constructors without default value.
     */
    public static final Object NO_DEFAULT = new Object();

    // ----------------------------------------------------- Instance Variables

    /**
     * The set of strings that are known to map to Boolean.TRUE.
     */
    private String[] trueStrings = { "true", "yes", "y", "on", "1" };

    /**
     * The set of strings that are known to map to Boolean.FALSE.
     */
    private String[] falseStrings = { "false", "no", "n", "off", "0" };

    // --------------------------------------------------------- Protected Methods

    /**
     * Return the default type this <code>Converter</code> handles.
     * 
     * @return The default type this <code>Converter</code> handles.
     * @since 1.8.0
     */
    protected Class getDefaultType() {
        return Boolean.class;
    }

    /**
     * Convert the specified input object into an output object of the specified type.
     * 
     * @param type
     *            is the type to which this value should be converted. In the case of this BooleanConverter class, this value is ignored.
     * 
     * @param value
     *            is the input value to be converted. The toString method shall be invoked on this object, and the result compared (ignoring case)
     *            against the known "true" and "false" string values.
     * 
     * @return Boolean.TRUE if the value was a recognised "true" value, Boolean.FALSE if the value was a recognised "false" value, or the default
     *         value if the value was not recognised and the constructor was provided with a default value.
     * 
     * @throws Throwable
     *             if an error occurs converting to the specified type
     * @since 1.8.0
     */
    protected Object convertToType(Class type, Object value) throws Throwable {

        // All the values in the trueStrings and falseStrings arrays are
        // guaranteed to be lower-case. By converting the input value
        // to lowercase too, we can use the efficient String.equals method
        // instead of the less-efficient String.equalsIgnoreCase method.
        String stringValue = value.toString().toLowerCase();

        for (int i = 0; i < trueStrings.length; ++i) {
            if (trueStrings[i].equals(stringValue)) {
                return Boolean.TRUE;
            }
        }

        for (int i = 0; i < falseStrings.length; ++i) {
            if (falseStrings[i].equals(stringValue)) {
                return Boolean.FALSE;
            }
        }

        throw new ConversionException("Can't convert value '" + value + "' to a Boolean");
    }

    /**
     * This method creates a copy of the provided array, and ensures that all the strings in the newly created array contain only lower-case letters.
     * <p>
     * Using this method to copy string arrays means that changes to the src array do not modify the dst array.
     */
    private static String[] copyStrings(String[] src) {
        String[] dst = new String[src.length];
        for (int i = 0; i < src.length; ++i) {
            dst[i] = src[i].toLowerCase();
        }
        return dst;
    }
}
